In the last decades, Mt. Stromboli produced four vulcanian eruptions, in 2003 and 2007 and July and August 2019, recorded by INGV monitoring network. Specifically, last three events are studied ...through records from borehole strainmeters, which allow to infer details on source dynamics. These events are preceded by a slow strain buildup, starting several minutes before the paroxysms, which can be used in future for early warning. Eruptions consist of two or more strain pulses, with oscillations ranging from several seconds, as in 2007, to some minutes, as in 2019, and lasting from several minutes to 1 hr after the explosions.
Plain Language Summary
Sacks‐Evertson borehole dilatometers are a special kind of strainmeter, capable of recording volumetric strain changes. In the current manuscript, data recorded by such an instrument reveal that strain changes occurred several minutes before two paroxysmal events occurred in the summer of 2019 at Stromboli, an open‐conduit volcano located in Eolian Islands, Italy. A comparison of 2019 paroxysms has been made with previous eruptions at Stromboli volcano: Similarities among the explosions suggest a common source mechanism. Starting from these observations, a real‐time early warning system could be developed in the future, allowing Italian Civil Protection Department to set up automated (or semi‐automated) variable alert levels, which could trigger alarms accordingly. Such an early warning system could then be used to provide alerts for other similar open‐conduit volcanoes.
Key Points
Borehole dilatometers are widely used to monitor open‐ and closed‐conduits volcanoes, recording areal strain changes due to volcanic sources
A dilatometer recorded strain changes minutes before eruptions onset for 2019 activity: Correlation with 2007 paroxysm suggests common source
For the first time a comparison high‐frequency, high‐sensitivity strain data for the 2007 and both 2019 vulcanian explosions are presented
For polyhedral mass bodies having arbitrary shape and density distribution of polynomial type we present a tensorial approach to derive analytical expressions of the gravitational potential and ...gravity vector. They are evaluated at an arbitrary point by means of formulas, referred to a Cartesian reference frame having an arbitrary origin, that are shown to be singularity-free whatever is the position of the observation point with respect to the body. The solution is expressed as a sum of algebraic quantities depending solely upon the 3D coordinates of the polyhedron vertices and the coefficients of the polynomial density function. Hence, no recursive expression needs to be invoked as in the recent contribution by Ren et al. (Surv Geophys 41:695–722, 2020). Moreover, the tensorial formalism developed in the paper allows one to obtain more concise, coordinate-free expressions that can also be extended to address polynomial functions of greater order. The analytical expressions of the gravitational potential and gravity vector are numerically validated and compared with alternative methods retrieved from the literature.
In the present work we report on the growth, spectroscopy and laser results of diode pumped Pr-doped LiYF(4), LiLuF(4) and LiGdF(4) fluoride, scheelite-type structure crystals. We measured the ...polarisation dependent absorption and emission properties as well as the decay time of the (3)P(0) level. Exploiting the (3)P(2) absorption around 444 nm, we obtained efficient laser emission under GaN laser diode pumping on several transitions from the green to the near infrared wavelength range.
Laser radiation has been used to cool matter ranging from dilute gases to micromechanical oscillators. In Doppler cooling of gases, the translational energy of atoms is lowered through interaction ...with a laser field. Recently, cooling of a high-density gas through collisional redistribution of radiation has been demonstrated. In laser cooling of solids, heat is removed through the annihilation of lattice vibrations in the process of anti-Stokes fluorescence. Since its initial observation in 1995, research has led to achieving a temperature of 208 K in ytterbium-doped glass. In this Letter, we report laser cooling of ytterbium-doped LiYF4 crystal to a temperature of ∼155 K starting from ambient, with a cooling power of 90 mW. This is achieved by making use of the Stark manifold resonance in a crystalline host, and demonstrates the lowest temperature achieved to date without the use of cryogens or mechanical refrigeration. Optical refrigeration has entered the cryogenic regime, surpassing the performance of multi-stage Peltier coolers.
We present a detection scheme to search for QCD axion dark matter, that is based on a direct interaction between axions and electrons explicitly predicted by DFSZ axion models. The local axion dark ...matter field shall drive transitions between Zeeman-split atomic levels separated by the axion rest mass energy m
c
. Axion-related excitations are then detected with an upconversion scheme involving a pump laser that converts the absorbed axion energy (~hundreds of μeV) to visible or infrared photons, where single photon detection is an established technique. The proposed scheme involves rare-earth ions doped into solid-state crystalline materials, and the optical transitions take place between energy levels of 4f
electron configuration. Beyond discussing theoretical aspects and requirements to achieve a cosmologically relevant sensitivity, especially in terms of spectroscopic material properties, we experimentally investigate backgrounds due to the pump laser at temperatures in the range 1.9 - 4.2 K. Our results rule out excitation of the upper Zeeman component of the ground state by laser-related heating effects, and are of some help in optimizing activated material parameters to suppress the multiphonon-assisted Stokes fluorescence.
Abstract
The pharmacological arsenal against the COVID-19 pandemic is largely based on generic anti-inflammatory strategies or poorly scalable solutions. Moreover, as the ongoing vaccination campaign ...is rolling slower than wished, affordable and effective therapeutics are needed. To this end, there is increasing attention toward computational methods for drug repositioning and de novo drug design.
Here, multiple data-driven computational approaches are systematically integrated to perform a virtual screening and prioritize candidate drugs for the treatment of COVID-19. From the list of prioritized drugs, a subset of representative candidates to test in human cells is selected. Two compounds, 7-hydroxystaurosporine and bafetinib, show synergistic antiviral effects in vitro and strongly inhibit viral-induced syncytia formation. Moreover, since existing drug repositioning methods provide limited usable information for de novo drug design, the relevant chemical substructures of the identified drugs are extracted to provide a chemical vocabulary that may help to design new effective drugs.
Abstract
Two paroxysmal explosions occurred at Stromboli volcano in the Summer 2019, the first of which, on July 3, caused one fatality and some injuries. Within the 56 days between the two ...paroxysmal explosions, effusive activity from vents located in the summit area of the volcano occurred. No significant changes in routinely monitored parameters were detected before the paroxysmal explosions. However, we have calculated the polarization and the fractal dimension time series of the seismic signals from November 15, 2018 to September 15, 2019 and we have recognized variations that preceded the paroxysmal activity. In addition, we have defined a new parameter, based on RSAM estimation, related to the Very Long Period events, called
VLP size
, by means of which we have noticed significant variations through the whole month preceding the paroxysm of July 3. In the short term, we have analyzed the signals of a borehole strainmeter installed on the island, obtaining automatic triggers 10 minutes and 7.5 minutes before the July 3 and the August 28 paroxysms, respectively. The results of this study highlight mid-term seismic precursors of paroxysmal activity and provide valuable evidence for the development of an early warning system for paroxysmal explosions based on strainmeter measurements.
Abstract
The COVID-19 disease led to an unprecedented health emergency, still ongoing worldwide. Given the lack of a vaccine or a clear therapeutic strategy to counteract the infection as well as its ...secondary effects, there is currently a pressing need to generate new insights into the SARS-CoV-2 induced host response. Biomedical data can help to investigate new aspects of the COVID-19 pathogenesis, but source heterogeneity represents a major drawback and limitation. In this work, we applied data integration methods to develop a Unified Knowledge Space (UKS) and used it to identify a new set of genes associated with SARS-CoV-2 host response, both in vitro and in vivo. Functional analysis of these genes reveals possible long-term systemic effects of the infection, such as vascular remodelling and fibrosis. Finally, we identified a set of potentially relevant drugs targeting proteins involved in multiple steps of the host response to the virus.
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